Combined piston-return mechanism

ABSTRACT

A brake actuating piston which includes a return mechanism for moving the piston to its at rest position when brake pressure is released. The piston moves in a cylindrical sleeve. A cylindrical spring holder surrounds the sleeve and is connected to the piston stem by a friction grip. A coil spring carried by the holder is compressed when the piston is moved toward the applied position and expands upon release of brake pressure to move the holder and the piston back to their at rest positions.

United States Patent 1191 Angelis et al.

1 1 COMBINED PISTON-RETURN MECHANISM [75] Inventors: William J. Angelis;Robert E.

Berger, both of North Canton; Robert E. Conkey, Barberton, all of Ohio[73] Assignee: The Goodyear Tire & Rubber Company, Summit, Ohio 22Filed: Mar. 31, 1972 [21] Appl. N0.: 240,183

52 us. or 92/130, 92/15, 188/196 P 51 1111.121. ..'...,-F0lb 31/00,F1511 15/26 [58] Field o1-Search 92/130, 15, 29, 417 R,

[56] References Cited I UNITED STATES PATENTS Kirk 92/130 1111 3,811,3661451 May 21, 1974 3,188,048 6/1965 Sutherland 91/130 3,331,289 7/1967.Horst 91/417 R 3,524,715 8/1970 Grantham 92/130 2,040,707 5/1936 Palmer92/130 Primary Examiner--Paul E. Maslousky Attorney, Agent, orFirm-Oldham & Oldham 5 7] ABSTRACT A brake actuating piston whichincludes a return mechanism for moving the piston to its at restposition when brake pressure is released. The piston moves in acylindrical sleeve; A cylindrical spring holder surrounds the sleeve andis connected to the piston stem by a friction grip. A coil springcarried by the holder is compressed when the piston is moved toward theapplied position and expands upon release of brake pres- I sure to movethe holder and the piston back to their at rest positions.

3 Claims, 2 Drawing Figures sum 1 or 2 PATENTEB m 2 1 mm 1 COMBINEDPISTON-RETURN MECHANISM The present invention relates to a brake pistonand more particularly to such a brake piston which is provided with anautomatic return mechanism.

The pistons of the present invention are intended for use with aircraftbrakes of the type having a stack of discs consisting of alternaterotating and stationary discscarried between a fixed back plate and anaxially movable pressure plate. In such brake installations, a pluralityof pistons arranged in a circular pattern engage the pressure plate tomove the pressure plate axially toward the back plate so that the discsare clamped tightly against one another toachieve braking action. lnsuch a braking assembly it is preferable that, upon release of brakingpressure, the piston be moved back to its at rest position so that thediscs may separate sufficiently to allow adequate cooling. Also, ifmeans are provided for moving the piston back to an at rest position,heat transfer through the pressure plate and brake pistons to thehydraulic fluid of the braking system is substantially reduced,resulting in increased life of the braking system. In prior arrangementsreturn springs have been attached directly to the pressure plate.However, with such arrangements the pressure plate is subjected tobending moments which decrease the effective life of the pressure plate.

It is the primary object of the present invention .to provide a brakepiston incorporating a return mechanism to bring the pistons to theirbrake released position immediately upon release of hydraulic pressure.

It is also an object of the present invention to provide a brake pistonand return mechanism assembly which eliminates the necessity ofmechanical attachment between the return springs and the pressure plate.

Another object of the invention is the provision ofa piston and returnmechanism which automatically adjusts for wear of the friction surfacesof the brake assembly.

A further object of thepresent invention is to provide a brake pistonand return mechanism assembly which may be economically fabricated andeasily assembled.

The above and other objects of the invention which will become apparentin the following detailed description are achieved by providing a brakepiston and return mechanism assembly which consists, essentially, of apiston, a cylinder sleeve in which the piston moves, a cylindricalspring retaining member surrounding the sleeve and connected tothepiston stem by a grip connection. a compression coil spring actingbetween the spring carrier and a fixed member, the spring beingcompressed upon brake actuation and expanding upon brake release to movethe piston toward its brake released or at rest position,'and a bearingplate for transmitting force from the end of the piston stem to thepressure plate of the brake assembly.

The above and other objects and advantages of the invention will becomeapparent upon consideration of the following detailed description andthe accompanying drawings wherein there is shown a preferred embodimentof the invention.

In the drawing:

HO. 1 is an elevational sectional view ofa brake piston and returnmechanism assembly constructed in accordance with the principles of thepresent invention; and

FIG. 2 is a fragmentary elevational view taken along the line 22 of FIG.I.

A wheel and brake assembly is designated generally by the referencenumeral and includes a stationary axle 12 to which is affixed a housing14 having splines 16 to receive the stationary brake discs 28 of a brakeassembly 20. Rotatably carried on the axle 12 is a wheel 22 which isprovided with splines 24 for engaging the rotating disc 26 of the brakeassembly 20, the discs 18 and 26 being interleaved with one another andcarried between a fixed back plate 28 and an axially movable pressureplate 30. The piston assembly 32 of the present invention engages thepressure plate 30 and,

' when actuated by suitable hydraulic pressure, forces the pressureplate axially toward the back plate 28 so that the discs 18 and 26 areclamped between one another and between the pressure plate 30 and backplate 28 to exert braking force.

As is conventional, a plurality of piston assemblies 32 are provided inthe housing 14, the assemblies being located in a circle concentric withthe axle 12. The housing 14 is provided with a cylindrical bore 34 foreach of the piston assemblies 32 and a cylinder sleeve 36 is received inthis bore and projects axially toward the brake disc assembly 20,Slidably received within the sleeve 36 is a piston 38, the bore 34 beingconnected by suitable ports tothe hydraulic pressure source to providepressure to the inner face of the piston 38. Suitable sealing means suchas the O-rings 40 and 42 are provided to provide a fluid type seal forthe bore 34. The piston32has a stem 44 which bears at its outer end 46against a plate 48 riveted or otherwise connected to the pressure plate30. Surrounding the proportion 50 of the cylinder sleeve 36 whichprojects from the bore.34 is a spring retaining member 52, the member 52being cylindrical and having an outwardly projecting annular flange 54at one end and extending inwardly towards stem 44 at the opposite end,as indicated at 56. A grip member 58 encircles and frictionally engagesthe piston stem 44 adjacent the inwardly projecting end 56 of the springretaining sleeve, the grip member being retained by a cup-like retainingplate 60 connected to the end 56 of the spring retaining sleeve 52. Acup-like outer housing sleeve 62 surrounds the spring retaining sleeve52 and has an outwardly projecting annular flange 64 which is retainedin the fixed housing 14 by a retaining ring 66. It will be noted thatthe cylinder sleeve 36 has an outwardly projecting annular shoulder 72which engages the upper end 64 of the outer sleeve 62 so that the sleeve36 is retained in place by the housing 62 and retaining ring 66. A coilspring is carried in the annular space between the spring retainingsleeve 52 and the outer housing 62, the spring bearing against theoutwardly projecting annular flange 54 of the spring retaining sleeveand the end portion 68 of the housing 62.

Upon actuation of the brake by any suitable control means hydraulicpressure supplied to the port 35 forces the piston 38 toward the brakestack assembly 20 so that the stem 44 engages the plate 48 forcing thepressure plate 30 toward the backing plate. As the piston 38 movestoward the brake assembly 20 the spring retaining sleeve 52 moves withthe piston compressing the spring 70 until the end 56 of the retainingsleeve 52 contacts the end 68 of the fixed idle housing 62. The grip 58permits continued movement of the piston 38 and stem 44.

Upon release of brake pressure the restraining force on the spring 70 isreleased and the spring 70 expands moving the retaining sleeve 52 towardits at rest position. The grip 58 engages the stem 44 of the piston 38so that the piston 38 is also moved back toward its at rest position.

It should be noted that the piston may move a greater distance towardthe brake assembly under the action of hydraulic fluid than it movesaway from the brake assembly under the action of the spring 70 since therange of travel of the spring 70 is limited. Any additional outwardmovement of the piston is necessitated by wear of the friction surfacesof the brake discs. By limiting the amount of return movement the:piston assembly is automatically positioned at the preferred point forreapplication of brake pressure, a minimum amount oflost motion beingnecessary before brake action is achieved.

While only the best known embodiment of the invention has beenillustrated and described in detail herein it should be understood thatthe invention is not limited thereto or thereby. Rather, modificationsand/or addi- V l. A brake piston and return mechanism assembly,

comprising:

a housing having a cylindrical bore;

a piston received within the bore and having a stem projecting coaxiallytherefrom;

spring means;

first and second connecting means for connecting the first and secondends of the spring means to the piston stem and the housing,respectively, whereby the spring means exerts an opposing force on thepiston stem when the piston moves toward its extended position; and

the first connecting means comprising a slidably positioned cylindricalsleeve located concentricly of the piston stem, having an outwardlyprojecting annular flange at one end which engages the first end I ofthe spring means, and operatively connected at the opposite end to thepiston stem for movement therewith, said sleeve is connected to thepiston stem by means of a friction grip connection permitting movementof the piston stem relative to the sleeve. 1

2. A piston and return mechanism assembly, comprising:

a housing having an open-ended cylindrical bore and port meansconnecting the bore to a fluid pressure source;

a piston received in the bore and having a stem extending coaxially fromthe bore;

a first cup-like sleeve concentric with the stem and having an outwardlyprojecting annular flange at the open end of the sleeve;

connecting means attaching the closed end of the sleeve to the stem; I

a second cup-like sleeve surrounding the first sleeve and connected atits open end to the housing;

a coil spring positioned between the first and second sleeves andbearing against the annular flange 0f the first sleeve and the closedend of the second sleeve; and i the connecting means comprises frictiongrip means permitting movement of the stem relative to the firstcup-like sleeve.

3. A piston and return mechanism assembly, comprising:

a housing having an open-ended cylindrical bore and port meansconnecting the bore to a fluid pressure source;

a piston received in the bore and having a stem extending coaxially fromthe bore;

a first cup-like sleeve concentric with the stem and having an outwardlyprojecting annular flange at the open end of the sleeve;

connecting means attaching the closed end of the sleeve to the stem;

a second cup-like sleeve surrounding the first sleeve and connected atits open end to the housing;

a coil spring positioned between the first and second sleeves andbearing against the annular flange of the first sleeve and the closedend of the second sleeve;

an open-ended cylindrical sleeve received within the bore and projectingpartially into the first cup-like sleeve, the piston being slidablyreceived in the cylindrical sleeve; and

the bore having an enlarged diameter outer portion,

the cylindrical sleeve having an outwardly projecting annular shoulderextending into the outer portion of the bore, and the open end of thesecond cup-like sleeve extending into the outer portion of the bore toretain the cylindrical sleeve in place.

1. A brake piston and return mechanism assembly, comprising: a housinghaving a cylindrical bore; a piston received within the bore and havinga stem projecting coaxially therefrom; spring means; first and secondconnecting means for connecting the first and second ends of the springmeans to the piston stem and the housing, respectively, whereby thespring means exerts an opposing force on the piston stem when the pistonmoves toward its extended position; and the first connecting meanscomprising a slidably positioned cylindrical sleeve located concentriclyof the piston stem, having an outwardly projecting annular flange at oneend which engages the first end of the spring means, and operativelyconnected at the opposite end to the piston stem for movement therewith,said sleeve is connected to the piston stem by means of a friction gripconnection permitting movement of the piston stem relative to thesleeve.
 2. A piston and return mechanism assembly, comprising: a housinghaving an open-ended cylindrical bore and port means connecting the boreto a fluid pressure source; a piston received in the bore and having astem extending coaxially from the bore; a first cup-like sleeveconcentric with the stem and having an outwardly projecting annularflange at the open end of the sleeve; connecting means attaching theclosed end of the sleeve to the stem; a second cup-like sleevesurrounding the first sleeve and connected at its open end to thehousing; a coil spring positioned between the first and second sleevesand bearing against the annular flange of the first sleeve and theclosed end of the second sleeve; and the connecting means comprisesfriction grip means permitting movement of the stem relative to thefirst cup-like sleeve.
 3. A piston and return mechanism assembly,comprising: a housing having an open-ended cylindrical bore and portmeans connecting the bore to a fluid pressure source; a piston receivedin the bore and having a stem extending coaxially from the bore; a firstcup-like sleeve concentric with the stem and having an outwardlyprojecting annular flange at the open end of the sleeve; connectingmeans attaching the closed end of the sleeve to the stem; a secondcup-like sleeve surrounding the first sleeve and connected at its openend to the housing; a coil spring positioned between the first andsecond sleeves and bearing against the annular flange of the firstsleeve and the closed end of the second sleeve; an open-endedcylindrical sleeve received within the bore and projecting partiallyinto the first cup-like sleeve, the piston being slidably received inthe cylindrical sleEve; and the bore having an enlarged diameter outerportion, the cylindrical sleeve having an outwardly projecting annularshoulder extending into the outer portion of the bore, and the open endof the second cup-like sleeve extending into the outer portion of thebore to retain the cylindrical sleeve in place.